1. Field of the invention
The present invention generally relates to an image input apparatus for inputting image information of an imaging object. More specifically, the present invention is directed to such a compact/low-cost image input apparatus operable under low power consumption without employing a buffer memory, while driving a CCD only during an imaging operation.
2. Description of the Related Art
While high grade type personal computers are commercially available and are popularized, various image applications such as television telephone, video mails, and electric albums are normally used. As a result, image input apparatuses used for personal computers, known as digital cameras, are gradually popularized. On the other hand, portable terminals such as notebook type personal computers and PDAs are developed, and are commercially available. Recently, cameras are connected to these portable terminals, or are assembled into these portable terminals. These cameras operable with the portable terminals must be made compact for the sake of portability thereof. In addition, since these portable terminals are mainly operated by batteries, the power consumption thereof must be reduced. Furthermore, since cameras are assembled into PHS and portable telephone, cost of these portable terminals must be lowered.
In one typical conventional image input apparatus used with a personal computer, there are provided; a lens for forming image light of an imaging object; a CCD for receiving the image light transferred from this lens; an A/D converter for converting an analog image signal derived from this CCD into digital image data; a buffer memory device for temporarily storing the digital image data derived from this A/D converter; an interface control unit for reading the digital image data from this buffer memory device to convert this read image data, and for transferring this converted image data to a personal computer; and further a drive control unit for controlling drive operations of these units.
However, the above-described conventional image input apparatus owns the following problems. That is, in the conventional image input apparatus for the personal computer, both the CCD and the A/D converter are driven in the constant time period to read the image data, whereas the transfer clock used between this image input apparatus and the personal computer is not produced in a constant time period, due to the load variation of the CPU. As a result, the buffer memory device capable of storing thereinto the image data is necessarily provided between the A/D converter and the interface control unit. Accordingly, this conventional image input apparatus for the personal computer is not suitable for compact/low power consumption/low cost aspects.